


Gaining Understanding

by toomanydewgongs



Category: Fire Emblem Series, Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: F/M, Fire Emblem - Freeform, LEWD, Romance, S Support, Sex, Shipping, Three Houses, byleth - Freeform, i bet they even hold hands, petra - Freeform, witness brigid pride
Language: English
Status: Completed
Published: 2019-08-13
Updated: 2019-08-22
Packaged: 2020-08-21 00:02:40
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,134
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20236567
Author URL: https://archiveofourown.org/users/toomanydewgongs/pseuds/toomanydewgongs
Summary: Byleth and Petra share a night together after the professor proposes to the princess.





	1. Chapter 1

"I am overflowing with the passion!" Petra could barely contain herself at this point. Only two hours had passed since she told Byleth how she had felt. Since she put on the ring he offered her. Since they truly began their lives together. It had only been two hours, yet for the Princess of Brigid, it had felt like an eternity. She indeed felt extremely passionate in this moment and had a strong desire to show her fiance how she truly felt.

Byleth had momentarily retreated to his quarters after the two of them expressed their love and promised themselves to each other. It was already rare enough for him to show emotion, let alone for him to cry tears of joy. He needed time to recover, which his new fiance had agreed to. He was on his bed, face buried into the soft pillow, barely able to process what had happened.

_I...I can't believe I did that. I can't believe I COULD do that. Petra..._

For the first time in a long time, the professor-turned-tactician felt an overwhelming happiness. Sure, the conflict in Fodlan was ending soon and the balance of power had been permanently shifted. Sure, a great many positive changes were coming to the people. These were things worthy of celebration. But Byleth was always putting others before himself. He never had time to think about how he was benefiting from a situation. For the past 6 years of his life, he was always thinking about Jeralt, or Sothis, or Rhea, or his students he cared so deeply for. He barely knew how to be a person, let alone how to be selfish. But he did know one thing: for one night, he was the happiest man in the continent and he, much like his partner, felt a strong desire to express that. 

Knock. Knock. Knock. 

Three slow knocks at his door. Everyone else was still celebrating in the dining hall. Byleth smiled. It could only be one person. 

He opened the door slowly. While this was normally something he did without even thinking about it, this time, it felt like the longest second of his life. Perhaps it was because of who was on the other side and what she meant to him now. This wasn't just greeting someone who needed to ask him something like usual. This was welcoming his wife into his room. 

"H-hello, Petra." He barely managed to utter as he gazed at her form. She had been a striking, powerful woman to him ever since they reunited so many months ago, but she was even more amazing to him now. She was wearing the same outfit as usual. 

_Good. _

Byleth never complained about seeing her like this. He of course knew it was a culturally significant outfit to Petra. It was the outfit of her kingdom's assassins and warriors. But it was also an outfit that exposed her belly, arms, and most of her legs. It helped that Petra's body was extremely athletic; more than likely a result of her constant hunting and training. It was perfect, especially for tonight.

Without a word, she immediately moved in for a kiss. As if their body chemistry synced up immediately, Byleth knew when to grab her by the back of her waist and push her towards him, hands firmly on her back. Their lips locked in an instant, immediately locking the two into a passionate, long kiss. It felt like a blissful eternity for the two young lovers. The warrior princess slowly withdrew, but ever so slightly, just so she could get a few words in before they began. 

"I am...I am understanding what I am supposed to do, but I am having the nervousness." 

Byleth gave a reassuring smile and embraced her in a deep hug. He whispered into her ear. 

"I am too, but I trust you." 

They kissed once more, this time even more passionately. Petra jumped onto Byleth, locking her legs behind him as they continued kissing. They quickly made their way to Byleth's bed, bumping into his chair and pile of books in the process. Petra jumped off of Byleth and onto bed, biting her lip as she motioned towards her breasts. Byleth obliged.

"Take me, Professor." 


	2. Gaining Understanding: Part Two

Something started to stir within Byleth. He was new to emotions in general and was trying to process what he was feeling now. It felt somewhat similar to anger, though it was more an intense anticipation he wasn't able to control rather than anything violent. He felt a hunger that kept growing. It needed to be satiated. 

That desire only grew more intense as Petra removed her top to reveal her breasts. The same purple marks that were under her eye and on her body were also under each tanned breast, almost indicating where Byleth should place his hands. The nipples were slightly perky, though the professor didn't know if this was due to arousal on Petra's end or if they were always like this. After all, he was an expert on warfare and tactical advice, not anatomy. That was probably more Manuela's area of expertise. 

"Take me, Byleth, now!" She screamed in excitement. Her face immediately went red; a strong mix of both embarrassment at the sudden shouting and arousal at exposing herself for the first time. 

The professor obliged with only a simple nod before he placed his hands on her body and began feeling her. She had always looked muscular, but now he could feel her tightly toned body for himself. Her abs in particular felt amazing to the touch; they felt like they were made of steel, like Byleth could lay on them and feel safer than he did in full plate mail. However, what he was really interested in was farther up. 

The professor couldn't tell what was happening to him anymore. Something within was taking over. 

"Oh Spirits!" Petra yelled as she felt him handle her breasts. For the first few seconds, his hands were cold and almost unwelcoming; more a reaction to them being touched by someone besides herself for the first time than anything else. She wanted him to continue, which he did without a word. What was once a soft but cold grasp became warm and slightly rough. The professor was enjoying this already. He played and fondled with her for a few more moments as she began to shake. It was obvious for both of them that this would be their first times. 

Byleth moved his head down suddenly and sucked on her left breast for only a few seconds; a move so sudden she shook even more. It was the first time she ever felt a tongue on them. It was a nice, wet and somewhat warm feeling as he licked for a few seconds and sucked shortly after. His teeth clenched her left nipple as he gently pulled up for only a moment. As he let go, he enjoyed watching her breast bounce, and Petra smile afterwards. She was feeling amazing and they had barely started at this point. 

"Petra, I'm going to do something I'm not used to." 

"Okay, I am having the faith in you, Love." 

Byleth kept his tongue out and licked the princess' body all the way down from her nipples, past her belly button, to her hips. As if he was suddenly a Casanova, he effortlessly removed her decorations and shorts, thanks in no small part to her lifting her legs to help. It was only another blissful moment before Petra felt her husband's tongue hit something she never thought it would. 

"Ah!" Was all she could let out before Byleth began licking her vagina, trying his absolute best to be gentle. He had no idea what he was doing yet despite his inexperience, seemed to be hitting the right spot. His tongue gently massaged her as it made an up and down motion several times. She was already wet before he began but now could barely contain herself. She closed her eyes and squeezed her breasts as she let out a moan. This seemed to stir Byleth even more as he began licking her more and more. With each lick, Petra moaned, the two of them in an almost perfect unison. 

After half a minute of what felt like eternal bliss, Petra grabbed Byleth so that their eyes could lock. Both of them were already tearing up just a little; both out of nervousness and genuine affection for each other. "Byleth, please, take me now. I can not do more of the waiting!" 

He moved in to kiss her quickly and to get himself in position. He was being his usual quiet self again, but perhaps this was a sign of confidence on his part? All he knew was that he needed to tell her how much he loved her, and this seemed like the best way at this point. As he positioned himself, Petra began tearing off his clothes so that the two of them could be naked together. She was already feeling more of him than intended but now she could see and feel everything. Despite demanding he enter her, she reached forward for his hard penis and began grasping it. It was awkward for just a few seconds yet pleasure seemed to come more naturally to her than it did Byleth.

Within ten seconds of awkward fumbling, she was able to grasp it firmly yet not too firmly and move her hand back and forth. 

"Am-Am I doing the pleasuring correctly? I don't know if I am-" 

She was interrupted by Byleth grabbing her head. Despite the sudden move, she did not resist at all. She was ready to be 100% his for the night. And 100% his was what he intended. He grabbed her head and moved it forward and, as if she knew what he wanted, she opened her mouth and began sucking him off. She didn't know what to feel at first. Was this disgusting? Was this unwarranted? Was this...pleasurable? After a few seconds, she knew her answer and began sucking him off with all of her might. Byleth removed his hands from the back of her head as she started sucking on her own, passionately and quickly. She didn't know she was capable of such hard and fast pleasure, nor did Byleth know he was already at his limits. 

"Oh Goddess, wait Petra, I-" 

He unloaded immediately and without warning. He was moaning loudly, incapable of controlling himself. He felt a strong mixture of both pleasure and embarrassment. That is, until he looked down to see Petra not moving an inch despite nothing keeping her there. 

"Mmmmm." She managed to utter, his cock still in her mouth. She was sucking up everything Byleth was giving to the point that her throat was bulging from the climax; likely due to Byleth's natural constitution and this being his first time ever climaxing. There was naturally a lot of "build up" over the years. 

"Petra, oh Goddess, I am so so-aaaah." His plea was interrupted by her continuing to suck up the last of his cum. She looked perfect to him in this moment. And he felt perfect. But he wasn't finished and she seemed to know that. 

"I am happy that I made you happy, Byleth. Now we can really begin without having to worry about you accidentally doing that during the sex." 


	3. Chapter 3

The young and virile professor wanted to comply, of course, but given recent events, was unable to. A mix of fatigue, excitement and shame washed over Byleth though the same couldn't be said for Petra. While Byleth looked down at himself, somewhat frowning at his low constitution, Petra seemed more than pleased with the situation. Her usual confidence was showing. She gulped the last of his cum down and smiled, all of it seemingly absent from her face now.

_By Seiros, I am the luckiest man in the world._

"What is wrong, Byleth? It is my understanding that men like this sort of thing. I am not lying when I say that I am liking it too." She blushed again. Between her playful expression, choice of words and overall appearance, it would only be another minute or so before Byleth was ready to continue. All feelings of shame and doubt were immediately replaced with amorous excitement. 

"No, nothing's wrong. I'm just not setting a very good example right now is all. I will do much better in a second." He uttered as he returned to his surprisingly clean bed. 

Both of them embraced in a tender hug for a minute, their naked bodies finally touching. They felt warm, comforting and loving to each other.

"Okay..." The professor bluntly stated as he gazed at Petra one more time before continuing. She was completely naked now. Her tan skin and purple markings were a stark contrast to the rest of the room. She had a mark underneath her eye, several on her arms, one on her waist...and apparently one on her left buttcheek. It demanded to be slapped for its existence in such a spot which Byleth was happy to oblige. Petra gasped; his slap was firm but welcomed. 

With that out of the way, the Brigid assassin laid on her back, ready for her lover. She opened her legs, giving Byleth a seductive gaze as if she was silently demanding him. Byleth was bad at reading people, but could at least understand this situation and complied silently. 

As soon as he penetrated her, she gasped. _So this is what the first time feels like. _Petra had to admit, there was some slight pain involved. She had studied up on this long before this night, as she had been curious about having sex with several of her Black Eagle students like Caspar, Hubert and Dorothea, but no amount of reading could prepare you for the first moment of penetration. 

On Byleth's end, he felt like she was suffocating him down there...and it felt amazing. He knew that wasn't actually the case, as much like Petra, he too read up on the subject. To be completely honest, he was also interested in the subject as much as any young person surrounded by incredibly attractive people would be. For a moment, it felt too good. The brief friction was almost too much for him and Petra would have had to be blind to not notice his eyes roll up for a moment. However, he refused to allow his excitement to overtake him a second time. He was a fast learner, and managed to suppress his desire to cum again. 

With a renewed focus, he began thrusting into Petra. Each thrust was only a second long, but felt eternal in those moments. Each one brought up a different memory. With the first thrust brought up their first chance meeting with each other. The second thrust brought up their first real conversations as friends. The third thrust, a moment in a battle where Petra parried a blade that was meant for an unaware Byleth. The fourth thrust, a battle during the war where a wall of fire saved Petra from a demonic beast. Similar memories occurred with similar thrusts for a long and passionate five minutes. At the two minute mark, Byleth's speed and intensity of each thrust continued and he pushed himself further down on Petra, forcing her to raise her legs high in the air. After the first five minutes, Byleth wanted to switch things up. They tried to speak as they continued. 

"I...need you to..." He couldn't even finish his exhausted sentence before Petra was moving as if reading his mind. 

"No...need...I...am..." They could barely speak between his continued thrusts. With how wet she was, she was seemingly welcoming his hard cock to go as far as he could with as much ease as possible. 

She briefly exited him to turn over. Now, on her knees, she arched her back farther up, her rear facing Byleth now. He placed both hands on her buttcheeks, slapping the mark on her left side again as he entered her once again. This time he pushed with even more intensity as last time, the angle helping him move more with less effort. In turn, Petra welcomed his thrusts by shifting her body in tandem with his thrusts. She needed him to reach as far as he could inside her. She was craving his cock at this point as much as he was craving her. 

This continued for a few minutes, and similar to last time, each thrust brought its own memory. It wasn't long before Byleth, still weak in constitution and inexperience, was getting ready to cum again. Petra, in turn, was also getting ready. While true that it wasn't taking either of them very long, it was their first time, or at least that's what they were telling themselves. 

"Byleth, I am...I am..." She struggled to speak through his thrusting.   
"Me too."   
"Then...let me finish...then you can..." 

Byleth's thrusting intensified. He was ready to completely exhaust himself and spend all of his energy on the next minute. Thankfully his efforts were not in vain as Petra suddenly convulsed. 

She grabbed both of her tits firmly and began shaking while Byleth continued to thrust. "Don't stop!" He was getting exhausted but complied. Her shaking continued for another few seconds as she moaned loudly. She felt so many emotions and so much energy letting itself out in those moments. Byleht couldn't hold it back anymore. He thought at first he would just burst right then and there, but he controlled himself long enough for Petra to finish shaking before he positioned his dick right on her head. At first, he thought he would cum on her, but Petra wanted to swallow him again and wrapped her mouth around his cock, sucking passionately. He only lasted for three seconds before unleashing a second load into her mouth. 

...

Exhausted breaths permeated the air from the two of them. They were sweating, tired, and passionately in love with each other. They sat on Byleth's bed, sweating and naked from their rigorous exercise, just staring at each other in silent bliss. 

"I...I love you so much, Petra. I can't wait to do that with you in the morning." 

Petra let out a surprised gasp. "The morning!? You are..most eager."   
"Do you object?" 

She gave a playful smile and hugged her new husband. "Of course not. I am eager to be doing this with you each and every day for the rest of our lives. I love you, Byleth, and I always will."   
He returned her expression with a smile of his own. "Me too, Petra. I love you." 


End file.
